I put Eri....I guess because I can see her commanding respect from the BO and being Vermouth's BFF. And I also find it funny when I think of her wondering if she should sic Gin on him for flirting with girls right in front of her. V:

someone between :
yoko okino : vermouth may be her older sister or mother or best friend.
Mori kogoro . In the episode 345 :

It looks like I have given you too much freedom. Come back to my side, Vermouth

how the boss knows about the showdown between jodie and vermouth ?? Also I have to point to something the name of BO gives the name of the boss may be moriarity ( sorry if the name is wrong >_< ) in sharlock holmes . So don't miss that. "Mori " sounds like "mourir" the french word for "to die "
. The manager of coffee poirot : the boss is someone who uses clever codename , passwords etc.. based on mysteries and history may be ano kata has interest in mysteries and detectives

someone between :
yoko okino : vermouth may be her older sister or mother or best friend.
Mori kogoro . In the episode 345 :

It looks like I have given you too much freedom. Come back to my side, Vermouth

how the boss knows about the showdown between jodie and vermouth ?? Also I have to point to something the name of BO gives the name of the boss may be moriarity ( sorry if the name is wrong >_< ) in sharlock holmes . So don't miss that. "Mori " sounds like "mourir" the french word for "to die "
. The manager of coffee poirot : the boss is someone who uses clever codename , passwords etc.. based on mysteries and history may be ano kata has interest in mysteries and detectives

1) We got insight of the boss's character and the way he thinks and we know that he is infact stupid, the bar case shows that, since the whole case was Kogoro thinking, that means that that was real and not fake acting like some people say, so it doesn't make any sense.
2) The boss ordered his own assassination.
Also the boss just said that he has given Vermouth too much freedom, that doesn't tell us that he knew about the events that happened, he just knew that Vermouth was acting on her own(from Gin and Vodka).

IMO Shiro Suzuki is a possible candidate, and here's why:
Gosho Aoyama said that if the real name of the BO was revealed, it'd be easy to figure out who the boss is. If the Organisation is by any chance the Suzuki Corporation (and if the Black Organisation is literally just a crime syndicate out to make money), then it's CEO (Shiro Suzuki) would be the boss.

"I know that some unkind declarations were made, of rash vows and unspeakable things"
"But don't you know? When the rain lets up, you'll find that we belong to each other still."
"Apologies? What is that between us? Words cannot bridge what words could not break."
"Let's wipe the gunk off our clothes, the warm trails from our cheeks, and smile once again."